1. Field of the Invention
The present invention relates to an internal combustion engine having a lubrication structure for circulating oil.
2. Description of Background Art
An internal combustion engine is known wherein a lubrication structure is provided for circulatorily supplying oil to sliding parts. In such an internal combustion engine, a structure has been adopted in which the oil is supplied to the sliding parts (e.g., a generator, a cam chain, etc.) by use of an oil pump. The oil lubricates the sliding parts and flows down into an oil sump chamber provided at a lower part of the crankcase. The oil that flows down into and is reserved in the oil sump chamber is pumped up by the oil pump, and is again circulatorily supplied to the sliding parts. See, for example, Japanese Patent Laid-open No. 2005-61386.
In order to maintain the lubricating performance of oil, it is preferable to prevent bubbles from being contained in the oil. However, in the above-mentioned lubrication structure for circulating the oil to the sliding parts bubbles may be mixed into the oil during the oil flows down. Thus, the bubbles mixed in the oil in the oil sump chamber may be pumped up by the oil pump. More specifically, when the splashed oil comes directly into an oil introduction port of the oil sump chamber, the splashed oil impinges on the oil being reserved, making it easier for the bubbles to mix into the oil.